Quantitative permeability changes and the role of lung histamine in the alveolar capillary membrane (ACM) leak syndrome associated with endotoxin, hemorrhage, and ethchlorvynol have not been fully detailed. Employing the in vivo saline-filled dog lung model we will 1) Characterize the normal ACM permeability to graded narrow range dextrans (molecular radius 20 to 75 A degrees), urea and albumin. Normal lung liquid histamine will be determined. 2) Following endotoxin and ethchlorvynol injection and acute hemorrhage, determine the changes in permeability for graded dextrans compared to normal. Histamine levels in the lung and blood will be measured before and after various insults and 3) Attempt to block histamine release with DSCG or H1 and H2 receptor blockers (with chlorpheniramine and metiamide respectively) prior to the various insults and determine ACM permeability and histamine release. Employing the above protocol the role of histamine in the ACM leak associated with endotoxin, ethchlorvynol and hemorrhage will, hopefully, be elucidated.